The major causes of hyperuricemia are increased production and decreased excretion of uric acid. The former is mainly caused by overproduction of uric acid by xanthine oxidase (hereinafter also referred to as X.O.). On the other hand, the latter is increased renal tubular reabsorption of uric acid and the main mechanism is upregulation of human uric acid transporter (hereinafter also referred to as URAT1). Since uric acid is slightly soluble in water, that causes hyperuricemia. When uric acid in blood gets excessive, crystalline uric acid precipitates in the joints and so on and that causes an acute attack of arthritis (gout) or chronic changes in bones and joints. Furthermore, complications such as urinary calculi and renal insufficiency (gouty kidney) become, a problem.
Currently, as therapeutic agents for gout and hyperuricemia, alloprinol, a X.O. inhibitor, is widely used. In addition, other therapeutic agents for hyperuricemia having a X.O. inhibitory effect are disclosed in Patent references 1 to 4. Benzbromarone having an inhibitory effect of uric acid reabsorption (an uricosuric effect) is also used. As another agent, probenecid is illustrated, but it is not frequently used due to its weak activity. In addition, biaryl compounds or diaryl ether compounds described in Patent reference 5 are reported as agents having an uricosuric effect.
[Patent reference 1] Japanese Patent No. 3399559 specification.
[Patent reference 2] Japanese Patent No. 3220987 specification.
[Patent reference 3] Japanese Patent Publication No. 2002-105067 gazette.
[Patent reference 4] International Publication No. WO03/064410 pamphlet.
[Patent reference 5] Japanese Patent Publication No. 2000-001431 gazette.